The present invention generally relates to footwear and, more particularly, to footwear that provides increased stability, cushioning, and, further, that facilitates an enhanced performance for the wearer of the footwear.
When running, a runner's foot transitions through three phases of contact with each stride. Initially, a runner's foot typically lands on its heel. As a result, the heel experiences a significant impact or shock, which is absorbed by the heel bone (calcaneum). Because this is a dynamic force, the impact on the heel can be multiples of the runner's body weight. Furthermore, this impact is transmitted up toward the runner's leg joints.
The second phase initiates when the runner's body weight shifts forward. When the runner's body weight shifts forward, the force shifts away from the heel towards the middle portion of the foot. In addition, the arch of the foot spreads out, with the sole taking up the entire weight of the body. Then the foot rolls toward the metatarsals, which creates a torsional twisting effect due to asymmetrical nature of the foot, including the varying lengths of the toes. This may cause the foot to tilt toward to the inside (medial portion) of the foot or to the outside (lateral portion) of the foot placing additional strains on the joints and ligaments.
As the foot continues to roll forward and the runner's weight is transferred to the forefoot and the metatarsal bones, the force exerted is actually increased to and in some cases several multiples of the runner's body weight. This stress is distributed across the whole width of the forefoot by the muscles, ligaments, and tendons across the metatarsals.
In an attempt to reduce the impact forces on knees and ankle joints, current shoe designs incorporate a wide variety of means to cushion the foot. For example, some athletic shoes include air pockets that are incorporated into the sole of the shoe. However, some researchers believe that some cushioning can actually increase the impact forces. Others believe that not only can cushioning actually lead to an increase in the impact on the wearer's joints but it may also put the wearer at greater risk for injury.
Other problems addressed by shoe manufacturers, especially athletic shoe manufacturers, include reducing ankle strain due to over rotation. Typically, the ankle is one of the most vulnerable joints in the body, especially when engaging in athletic activities. Ankle sprains occur usually from excessive rotation of the ankle joint—both inversion and eversion rotation of the ankle joint. Further, it is believed that one most likely to incur an ankle sprain injury during the initial contact phase, known as the Passive contact phase; in which the ankle joint rotates through plantar-flexion and on into a dorsi-flexion rotation. In an attempt to reduce the risk of ankle injury, athletic shoe manufacturers have designed footwear that restricts both medial and lateral motion of the ankle to thereby limit both internal and external rotation of the ankle. However, by restricting the ankle motion, shoe manufactures often hinder the natural motions of the foot and ankle, which tends to reduce the user's athletic performance.
Consequently, there is a need to provide footwear that reduces the risk of injury to the wearer, especially to the wearer's ankle, and in a manner that enhances the wearer's performance, whether that performance is an athletic activity, such as running, playing basketball, playing tennis, hiking, playing racket ball, or a non-athletic activity, such as standing, for example at work, therapeutic exercises, walking, orthotics, or the like.